Automatic telephone system



March l5, 1932. N. H. sAuNDERs 1,849,694

AUTOMATIG TELEPHONE SYSTEM Original Filed Jan. 25. 1930 5 Sheets-Sheet lInu-sn DP Nurmau H. Saunders March 15, 1932. N. H. sAuNDERs AUTOMATICTELEPHONE SYSTEM Original Filed Jan. 23, 1930 5 Sheets-Sheet 2 s n QNf\W- n ml- .d mn Y N ma, R W ...m m. w HE i gm. `mmw\ w Gm "ww QS, EH mmmhuw @im u h mt m uw l N. l@ f S Rm, .1 lla.. HWmQN QN@ .I/wmwmmwoo NQNum a VITQMMQMMNQR mwN NWJIIIIMQWN. www www @NN @mmf mw Num. www? WN mmN@www N5 fw mw @Y l 1% QC Rw www RN Sm @NN an @u @QN 190| l@l QN @M m. QSm @Ik March 15, 1932. N. H. sAuNDERs 1,849,694

AUTOMATI C TELEPHONE SYSTEM Original Filed Jan. 23, 1930 5 Sheets-Sheet,3

March 15, 1932. N. H. sAuNDERs 1,849,694

AUTOMATIC TELEPHONE: SYSTEM Original Filed Jan. 23. 1930 5 Sheets-Sheet4 "ai il Nnrman H. Eaunders March l5, 1932.

N. H. sAuNDERs 1,849,694

AUTOMATIC TELEPHONE SYS'I-El Original Filed Jan. 23, 1930 5 Sheets-Sheet5 Nnr man H. 5 aum-lars Patented Mar. 15, 1932 UNITED STATES PATENToFF-ica NORMAN H. SAUNDEBS, OF HOMEWOOD, ILLINOIS, ASSIGNOR, BY MESN EASSIGNMENTS T ASSOCIATED ELECTRIC LABORATORIES, IN C., 0F CHICAGO, i

IORATION OF DELAWARE AUTOMATIC TELEPHONE SYSTEM Application led January23, 1930, Serial No. 422,906. Renewed September 25, 1931.

. The present invention relates in general to automatic telephonesystems, but more particularly to such systems in which line tinders areemployed to connect an idle selecting switch with a calling line; andthe principal object of invention, briefly stated, is the production ofnew and improved circuit refinements in finder switch systems, theimprovement tending to make the system more reliable, to give uniformhigh quality service, and to make it cheaper to install and maintain.

As a further object of the invention, a new and improved allotter ordistributor is provided which tests for a certain potential before thepreselected finder-selector link is taken into use responsive to a calland whlch allotter, in case such potential'is not found due to thefinder-selector link being off-normal or faulty, causes a newfinder-selector link to be selected. Y

As a further object, the allotter is provided with a timing device whichoperates within a predetermined time, in case the allotter fails tokick-off and select a new finderselector link, to operate a supervisoryalarm signal, to lock the allotter out of service until the exchangeattendant operates a key, and to transfer calls normally handled by thisallotter to its associated allotter in the other 3o group As a furtherob]ect, a new and improved circuit is provided for simultaneouslytesting two sets of contacts, the improvement insuring a positivestopping on a set of contacts if one of the lines of the set iscallingeven though the other is not calling.

urther objects not specically mentioned here will best be understoodfrom reading the detailed description and claims which follow.

The drawings comprising Figs. 1 to 5, inclusive, when arranged withFigs. l, 2, and 3 from left to right in a straight line, with Figs. 4and 5 placed beneath, and with correspondingly numbered lines inalignment, show sufiicient details to'enable a clear understanding ofthis invention.

Referring now to Fig. 1 in more detail, the selector SA shown on theleft-hand side is of the old and well known type of Strow- 50 gerselector to be included in a finder-selector link. The finder switch FAis of the Strowhaving wipers which are moved first direction to selectthe contacts of a calling 55 line. The wipers of the finder are shown onthe left-hand side of Fig. 2. Since in the present embodiment of thisinvention a finder switch of two-hundred line capacity is being used,the switch FA is provided with two 6o sets of wipers, the wipers 230 to232, incluslve, forming one set of wipers and the wipers 233 to 235,inclusive, the second set. The finder switch FA is also equipped with avertical test wiper 262, shown in the lower c5 left-hand corner of Fig.2.

In Fig. 2 i shown the subscribers lines S and S, it being assumed forthe purpose of illustration that the subscribers S line number 1s 125,and that the subscribers S line 'I0 number is 2 95. 'Associated witheach line are the usual lme and cut-ofi relays, the circuit of whichhave been modified in accordance wlth the objects of the presentinvention. The normal connections from the connector banks are alsoshown extending to the line and cutoff relays associated with thesubscribers lines S and S. In the lower part of Fig. 2 is shown thevertical banks VA and VB, which together with the wipers 262 and 263determine So the vertical designation to which the finder switches areto be operated.

In Fig. 3, there is shown the finder switch FB and selector SB, bothswitches being duplicates of those shown in Fig. 1 and, there- 85 ttore,need not be explained in detail at this une.

In Fig. 4, there is shown the finder allotter A comprising the steppingmagnet 407 and Wipers 408 to 410, inclusive, which allots the finders ofthe A group, that is the group containing the finders, such as finderFA, for use one at a time. Associated with this finder allotter are thecontrol relays 401 to 406, inclusive, the functions of which will bebest mderstood from the description which folows.

In Fig. 5, there is shown the finder allotter DB comprising the steppingmagnet 507, the wipers 508 to 510, inclusive, and associated relays 501to 506, inclusive. This allotter is a duplicate of that shown in Fig. 4,and allots the finders of the B group for use one at a time.

Throughout the drawings, have shown a plurality of batteries to avoidunnecessary com lications. In actual installation there wou d be but onebattery, preferably with its positive pole grounded.

In order to enable a clear understanding of the invention it will now beassumed that the subscriber S initiates a call, and it will be furtherassumed that the finder FA has been preselected by the finder allotterDA in readiness to handle the call. .Responsive to the removal of thereceiver from the switch hook at the substation S, line relay 201associated with line S is energized to mark that line busy in theconnector bank terminals, to mark the line calling in the finder banksto render it selectable by placing a battery potential thereon throughthe winding of the cut-off relay 202, and to place ground upon the startconductor 250. The grounding of conductor 250 places ground on thesecond contacts in the banks VA and also closes a circuit for the startrelay 406 in the linder' allotter DA. In case both the selector S'A andthe inder FA are in normal position the relay 404 in the finder allotterDA is energized to complete the start circuit for the finder FAwhereupon the finder is started in its vertical movement to hunt for themarking ground placed on the vertical banks VA. Since the calling line Shas a finder bank designation of 125 and, since the present call isassumed to be handled by the finder group to which that line is firstchoice, it will be necessary for the finder to take two vertical stepsto reach the level containing the calling line. The placing of ground onconductor 250 and the consequent marking of ground otential on thesecond bank contacts of the ank VA, will cause the finder FA to stop onthe second level, at which time its wipers will be rotated into thatlevel to pick out the contacts of the line, S. When the wipers arerotated into the level, tests will be made simultaneously by both setsof wipers, the lower set of wipers comprising wipers 233 to 235, willtest the line upon which they are resting, in this case line 121, and atthe same time the upper set of wipers comprising 230 to 232, inclusive,will test the line upon which they are resting, in this case line 221,and if neither one of these lines are calling both sets of wipers willbe stepped on to the next contacts where the test will be repeated. Whenthe line S is encountered, the battery potential applied to the testcontacts associated with that line will render it selectable,

thereby causing the finder FA to stop thereon and switch through so thatthe calling line will be connected through to the selector SA.

When the iinder switches through to the calling line the switching relayin the finder lock out relay is energized to operates and connectsground to the kick-oli' lead 181 extending to the allotter, whereuponthe allotter stepping magnet 407 is operated to cause the allotter topreselect another idle iin der-selector link.

The above general operation just described explains the normal operationof the finder and allotter. It may happen in some in' stances when afinder-selector link, such as that shown in Fig. 1, has been preselectedby an allotter and a call is initiated by a callin subscriber, such as-S, that the selector S may be in an oli-normal condition or thetinder-selector link may be faulty. In this case when the start relay406 in the allotter is enerized responsive to the call the test relay404 1n the allotter will not find negative battery on the guard lead 179and this relay, therefore, will not energize to close the start circuitthrough to the iinder-selector link. Relay 403 in the allotter energizesin thiscase and closes a circuit through its lower winding for operatingthe steppin ma et of the allotter to step the allotter o of t isfinderselector link` to select a new finder-selector link, after whichthe call may be proceeded with in the same manner as described.

In some instances due to fault, the finder may fail to switch throughand free the allotter so that the allotter may preselect another finderlink. In case the finder fails to switch through within a predeterminedtime, a vibrating relay 402 in the allotter is initiated in its oeration responsive to the energization of t e start relay to prepare acircuit for the supervisory lock-out relay 401. The supervisory lockoutrelay 401 is a slowto-operate relay and, therefore, does not energizeuntil the vibrating springs 419 and 420 stop vibrating and arepermanently closed.

It may be mentioned that this ermanent closure is not completed until asu cient time has been allowed for the finder to switch through andrelease the start relay 406 to open the circuit of the vibrating relay402. However, in case the finder due to some fault does not switchthrough properly the supervisory bring in a su ervisory alarm so as tocall the attention o the attendant at the exchange to the trouble. Inaddition this supervisory lock-out relay temporarily renders theallotter DA and the nder-selector links, such as SA and FA, inoperativeuntil the trouble or fault is corrected b the attendant or until suchtime as all of t e finder-selector links, such as SB and FB, becomebusy, in which case the supervisory relay 401 is permitted to releaseand restore the allotter DA for use.

In the normal operation of this stem the allotter DA and thefinder-selector links, such as SA and FA in the A group normally handleall of the calls from the su scribers in the A grou that is thesubscribers, such as S in the group, to which the finders, such as i FA,have first choice.

The operation of the allotter DB and the finder-selector link, such asFB and SB of the B tions linst described for the A selector links and`allotter.

Having described the general operation of the system` a detaileddescription of its opgroup lindereration will now be explained.

Line S 'initiates a @all Assume now that the line S initiates a call.Responsive to the removal of the receiver a circuit maybe traced fromground at springs 206, conductor 254, through the switch hook, receiver,transmitter and calling device of substation S, conduct-or 255, contacts209, and through the winding of line relay 201 to battez-y.

Line relay 201, upon energizing over the above traced circuit, atarmature 207 applies a battery potential to the finder test contactsthrough the right-hand low wound winding of cut-olf relay 202. Theapplication of this battery to the best contacts of line 125 renders theline selectable to the finders, such as linder FA, which are of thebattery searching type, that is the finders search for a batterypotential to cut through instead of testing for an absence of ground orguarding potential. At armature 205 line relay 201 connects ground toconductor 250 to ground the second vertical bank contact in the bank VAand to complete a circuit extending from conductor 250 by way ofresistance 251, conductor 260, armature 430 and its working contact ofnormally energized busy common relay 405, winding of start relay 406,working contact of armature 429 and said armature, through interrupt-ercontacts 428 of the stepping magnet 407, and through the winding ofrelay magnet 407 to battery. Due to the high resistance of start relay406 the stepping magnet 407 is not energized over this circuit. Startrelay 406, upon energizing over the above traced circuit, at armature432 closes a circuit for slow to operate relay 403, which relay,however, is not energized at this time unless the test relay 404 failsto energize. At armature 433 start relay 406 opens a point in thepreselecting stepping circuit of magnet 407 at its resting contact andat its working contact closes a circuit through the upper Winding oftest relay 404; at armature 434 closes another point in the circuit oftestrelay 404; at armature 435 closes a circuit for maintaining the busycommon relay 405 energized; and at armature 436 closes a circuit for thevibrating relay 402. Relay 402 energroup, are similar to the generaloperagizes and starts the vibratory spring 420 in operation preparatorto completing the'circuit for energizing the supervisory lockout relay401 in case the finder does not switch llgough andopen the circuit ofstart relay The operation of test relay 404 depends upon whether thefinder-selector link in Fig. 1 is at norma-l. In this instance it willbe as` sumed that the finder-selector link is at normal and that acircuit is completed for the test relay 404 in the allotter as follows:from ground by way of armature 434, upper Winding of relay 404, armature425, Working contact of armature 433 and said armature, guard wiper 410,guard conductor 179, finder vert1cal olf-normal springs 141 andv itsresting contact, conductor 135, selector vertical contact 131, andthrough the resistance 130 to battery. Relay 404, upon energizing overthe above traced circuit, at armature 423 closes a circuit for operatingthe line relay 105 of selector SA; at armature and its resting Contactopens the energlzmg circuit of relay 403 before slow-to-operate relay403 has had time to energize, and at the working contact of armature 424completes the start circuit for the vertical magnet 114 of the finder.At armature 426 relay 404 completes a locking circuit for itself fromarmature 434 before armature 425 opens Vits original energizing circuitthrough its upper winding. The circuit for energizing the line relay 105of selector SA may be traced as follows: from ground by way of armature423,

Aresistance 450, operate wiper 409, operate conductor 178, negative lineconnector 134, armature 119 and its resting contact, and through theupper winding of line rela-y 105 to battery. Line relay 105, uponenergizing, at armature 132 disconnects ground from finder releaseconductor 136, and also from busy common conductor 177 at its restingcontact and at its working contact completes a circuit for the slow torelease relay 104. Release relay 104, upon energizing, at armature 160connects ground to release trunk conductor 135; at armature 128 and itsworking contact prepares a circuit for the vertical series relay 103 andvertical magnet 110, and at the resting contacts of armature 128 opensanother point to finder release conductor 136. The operation of armature128 maintains the circuit of the release magnet 112 of the selector andthe release magnet 113 of the finder open to prevent such magnets fromenergizing when the vertical off-normal springs in both the selector andfinder operate on the first vertical step of such switches.

When relay 404 at armature 424 completes the start circuit for verticalmagnet 114, the vertical magnet is operated over the following circuit:from ground by Way of armature 432, armature 424 and its workingcontact, start wiper 408, start conductor 180, armature -153 and itsAresting contact, armature 157, armature 142, armature 146 and itsresting contact, and through the Winding of vertical magnet 114 tobattery. Vertical magnet 114 operates and raises the wipers 230 to 235,inclusive, and vertical test wipers 252 one Vertical step. Verticalmagnet 114, upon energizing, and armature 147 completes a circuit forenergizing stepping relay 106. Vertical test wiper 262 in Fig. 2 is nowin engagement with the first vertical test contact of the vertical bankVA and since there is no ground potential on this first vertical bankcontact no circuit is completed for changeover relay 107. Stepping relay106 energizes and at armature 142 interrupts the circuit to the verticalmagnet 114 whereupon the magnet releases and in turn opens the circuitto stepping relay 106. Stepping relay 106, upon deenergizing, atarmature 142 again completes the circuit for the vertical magnetwhereupon the vertical magnet raises the wipers another vertical stepand at armature 147 again completes the circuit for the stepping relay106. When vertical magnet 114 releases responsive to the energization ofrelay 106 a circuit is completed for the changeover relay 107 which maybe traced as follows: from ground by way of armature 205, commonconductor 250, second vertical test Contact in vertical bank VA,vertical test wiper 262, conductor 174, armature 145, through the upperwinding of changeover relay 107, and throughthe winding of steppingrelay 106 to battery. Stepping relay 106 is held energized in serieswith changeover relay 107 until such time as changeover relay 10T isfully energized.

Changeover relay 107, upon energizing, at armature 143 prepares therotary testing circuit by way of switch through relay 108 and wiperswitching relay 109; at armature 144 completes a locking circuit foritself to grounded start conductor 180; at armature 145 opens theoriginal energizing circuit of changeover relay 107, as well as openingthe circuit of relay 106 thereby permitting the stepping relay 106 todeenergize; and at armature 146 transfers the start conductor 180 fromthe vertical magnet 114 to the rotary magnet 115. Stepping relay 106,upon deenergizing, at armature 142 closes an energizing circuit forrotary magnet 115 as follows: from grounded start conductor 180,armature 153 and its resting contact, armature 157, armature 142,armature 146 and its working contact, and through the winding of rotarymagnet 115 to battery. Rotary magnet 115, upon energizing, advances thewipers 230 to 235, inclusive, into engagement with the first contacts inthe second level and also rotates the vertical test wiper 262 out ofengagement with the contacts of the vertical bank VA. At armature 148rotary magnet 115 completes the circuit for stepping relay 106,whereupon that relay energizes. Further rotation of the wipers of thefinder FA are now dependent upon whether the test wipers 231 and 234encounter a negative battery potential or not. In case negative batterypotential is not on either of the test contacts with which the testwipers 231 and 234 are now in engagement neither the switch throughrelay 108 or4 the wiper switching relay 109 will be energized.Therefore, when the rotary magnet 115 energizes the stepping relay 106in addition to stepping the wipers and the stepping relay 106 in turnopens the circuit of the rotary magnet at 142, the ro- \tary magnet inturn will open the circuit of the stepping relay 106, whereupon thesteppingrelay deenergizes andagain closes the circuitior the rotarymagnet 115. This cycle of operation continues until one of the testWipers 231 or 234"encounters a negative battery potential.

Assuming that no other line in the second level of the finder bankterminals is calling, except subscriber S, then when the test wipers 231and 234 are rotated in engagement with the fifth set of contacts testwiper 234 will encounter a negative battery potential which is appliedthrough the right-hand winding of cut-off relay 202. When wiper 234encounters this battery potential, wiper switching relay 109 energizesover the following circuit: ground by way of armature 143 and its upperworking contact, upper winding of wiper switching relay 109, conductor173, test Wiper 234, the test contact engaged thereby, test conductor256, armature 207, and through the right-hand low resistance winding ofcutoff relay 202 to battery. Wiper switching relay 109 and .cut-offrelay 202 energize in series over the above traced circuit. The cutoffrelay 202, at armatures 206 and 209 disconnects'the line relay 201 andthe normal battery and ground connections from the subscribers lineconductors: and at armature 208 prepares a circuit a holding circuit forthe cut-off relay 202 including both of its windings and also prepares acircuit for guarding the linel from intrusion by way of the connectorbanks. Line relay 201, upon deenergizing, at armature 207 opens theoriginal enengizing circuit of the cut-off relay 202 and permits theholding circuit, including both windings of cut-off relay 202, to becomeef feet-ive; and at armature 205 removes ground from conductor 250.

Returning now to the finder FA and when wiper switching relay 109energizes in series with the cut-off relay 202, it should be stated thatarmature 157 operates before the other armatures and breakes the circuitto the rotary magnet so that there is no possibility of the rotarymagnet operating to step the wipers an extra step after the callingpotential has been encountered by test wiper 234. At armatures 154 and159 wiper switching relay 109 disconnects the upper set of wipers 230 to232, inclusive, and connects up the lower `subscriber S.

set of wipers 233 to 235, inclusive. At armature 155 switching rela 109completes a locklng circuit for itself rom grounded release t-runkconductor 135; a-t armature 155 completes an energizin` circuit forswitch through relay 108 farom grounded release trunk conductor 135; andat armature 156 connects said grounded release trunk conductor 135 toconductor 173 thereby shunting out the upper winding of wiper switchingrelay 109 and connecting guarding potential by way of wiper 234 and thebank contact with which it is associated` conductor 256, armature 208,and through the two windings of the cut-oli' relay 202 to battery formaintaining the cut-oli' relay in energized position and also by way ofarmature 208 and its make contact through the test terminal of line S inthe connector banks in order to guard against any connector from seizingthe line S at 4this time. The circuit for energizing the switch throughrelay 108 may be traced as follows: grounded release trunk conductor135, larmature 155, armature 155 and throu h the lower winding of switchthrough re ay 108 to battery. It may also be mentioned at this time thatthe break springs of armature 153 are adjusted to break before any ofthe other` armatures are operated in order to insure the opening of therotary magnet circuit to prevent an extra step in case the test wiper231 was the only Wiper encountering a calling potential. At armatures150 and 158 switch through relay 108 connects the line conductors oflines S through to line conductors 134 and 137 of the finder-selectorlink; at armature 151 closes a locking circuit through its lowerwinding; at armature 152 prepares a guarding circuit which at this timeis ineffective because wiper switching relay has been energized andopened this guarding circuit at the normally closed springs controlledby armature 156; and at the working contact of armature 153 connects thestarting ground through to the common kick-oil` conductor 181 forenergizing the stepping magnet 407 of the allotter DA. The circuit forenergizing the stepping magnet 407 may be traced as follows: from groundby way of armature 432, armature 424 and its working contact, startwiper 408, start conductor 180, armature 153 and its working contact,common kick-oli:` conductor 181, and through the winding of magnet 407to battery.`

When the switch through relay 108 connects the line conductors of thecalling line S to conductors 134 and 137 dial tone is connected by wayof normally closed cam springs controlled by cam spring 133, through thelower winding of line relay 105, resting contact of armature 123 andsaid armature, andl by way of conductor 137 and the wipers of the finderthrough the receiver of the calling When calling subscriber S hears thewell known dialtone,such subscriber will knowthat the finder has foundand connected with his line, and that he may now proceed to set up thedesired connection to the called party. It will be noted at line relay105, that the upper and lower windings of l1ne\re1a 105 are included ina loop circult including both the line conductors of lineS and thesubstation calling device. The calhng subscriber S now operates hissubstation calling device in accordance with the digits of the callednumber. When the first digit is dialled, the circuit of the line relay105 is intermittently interrupted to cause the line relay to fall back acorres ondingly number of times. Each time-it alls back, line relay 105opens the circuit of slow-to-release relay 104 and closes a circuitthrough the armature 132 and its resting contact, armature 128 andthrough series relay 103,. and through the winding of vertical magnet110 to battery. Release relay 104 is maintained ener ized duringimpulsing. By the operation 0% the vertical magnet 110, the wipers 116to 118, inclusive, are raised'opposite the desired level of bankcontacts. Series relay 103 operates upon the first impulse of currenttransmitted to the vertical magnet and it remains operated throughoutthe vertical movement. Upon operating, relay 103 prepares a circuit forstepping relay 102, which is closed at the vertical otlnormal contact121, interrupter contact 126 of rotary magnet 111 as soon as the switchmoves from its normal position. At armature 124, relay 102 closes ashort-circuit around switching relay 101 and at armature 125 prepares acircuit for rotary magnet 111. At armature 124 relay 102 also closes alockin circuit for itself independent of armature 12 of relay 103.

When relay 103 falls back at the end of the vertical movement, itcompletes the rotary magnet circuit from grounded release trunkconductor 135 by way of armature 127 and its rest-ing contact, armature125, and the Winding of rotary magnet 111 to battery. When the rotarymagnet operates it advances the wipers into engagement with the firstset of bank contacts in the selected level, and, at the end of itsstroke, it opens the circuit of relay 102. Relay 102 thereupon fallsback and opens the magnet circuit and a further point in its own lockingcircuit. The rotary magnet falls back when this happens, and againconnects up the stepping relay. If the first trunk line is busy, the steplng relay operates again by way of groun ed contacts engaged by testwiper 117, armature 120 and its resting contact, oli-normal sprin s 121,interrupter spring 126, and the win ing 0f stepping relay 102`tobattery. This same ground also maintains the switching relay 101short-circuited to prevent it from switchdeenergizes.

ing through on a busy trunk. Stepping relay 102 again closes the circuitof the rotary magnet whereupon the buzzer like action between steppingrelay 102 and rotary magnet 111 contlnues until an idle trunk isreached, an idle trunk line being characterized in this case by theabsence of ground potential. When an idle trunk is reached', relay 102does not reoperate as no further ground potential is encountered; andrelay 101, which has been short-circuited heretofore by the groundpotential on the test wiper 117, energizes from the grounded releasetrunk conductor 135 in series with relay 102 by way of off-normalcontact 121, and contacts 126. Relay 102 does not operate in series withswitching relay 101, owing to the relatively high resistance of relay101. Switching relay 101 upon energizing, switches the call through tothe next switch in the train from where the call is extended in a wellknown manner. It should be mentioned, however, that the switching relay101 is maintained for the duration of this connection and, therefore,said relay at armature 122 removes the ground potential from conductor136 so that the selector SA and linder FA will not release when the lineand release relays 105 and 104 deenergize when the selector SA switchesthrough. This selector circuit is a well known circuit with the additionof vertical off-normal spring 131 for maintaining battery potential onrelease trunk conductor 135 only during the time switch SA is in normalposition. It also containsa finder release conductor 136 for completingthe circuit to the release magnet 115 of the finder when the switchingrelay 101 is released at the end of a conversation. Returning now to theallotter shown in Fig. 4, and at a time when the stepping magnet 407 wasenergized responsive to the switch through relay 108 of the inderoperating to connect ground to the common kick-oit' conductor 181,magnet 407, upon energizing, at its interrupter springs 428 opens thecircuit of start relay 406 whereupon start relay 406 At armature 432relay 406 removes ground from a start wiper 408 thereby opening thecircuit of stepping magnet 407 to cause it to deenergize; at armature433 closes a stepping circuit for magnet 407, at armature 434 opens` thelocking circuit of test relay 404 whereupon the latter relaydeenergizes; at armature 435 opens one point in the circuit of busycommon relay 405 which relay, however, is maintained in energizedposition as long as an idle finder-selector link maintains ground on thebusy common lead 177; and at armature 436 opens the circuit eX- tendingto the vibrating relay 402 before the vibratory springs 420 havepermanently closed to prevent the supervisory lock-out relay 401 fromenergizing at this time.

Stepping magnet 407, upon deenergizing,

advances its wipers 408 to 410, inclusive, into engagement with its nextset of bank contacts leading to the succeeding finder-selector linksimilar to the finder-selector link shown in Fig. 1. In case saidfinder-selector link is in an oi-normal position and is busy thevertical oif-normal springs corresponding to vertical off-normal springs141 are operated to connect ground to the guarding con ductor, such asguarding conductor 179, which in this case will extend through thesecond bank contacts with which the test wiper 410 is now in engagement.rllhis ground connection will extend by way of start wiper 410, armature433 and its resting contact, armature 429, interrupter springs 428, andthrough the winding of stepping magnet 407 to battery. Magnet 407operates 1n a buzzer like manner as long as wiper 410 encounters busyground potentials, however, as soon as wiper 410 encounters a guardconductor leading to an idle finder-selector link the wipers of theallotter come to rest in corresponding positions to preselect this idlefinder-selector link for the next calling party. The finder allotter DA,therefore, preselects another idle finder-selector link as soon as thefinder with which it is associated has swltched through and establishedconnection with the calling line.

Since the finder FA is a 200 oint finder and, therefore, has two sets ofwipers it may so happen that the test wiper 231 instead of test wiper234' may encounter the negative battery calling potential of a callingline, while the test wiper 234 does not. In this case the finder isoperated in the same manner as previously described, and wat n wiper 231encounters the negative battery potential on the test contactsassociated with the calling line a circuit will be completed foroperating the switch through relay 108 alone as follows: from ground byway of armature 143 and its lower make contact, upper winding of switchthrough relay 108, conductor 172, and through test wiper 231 to negativebattery. The circuit extending through the upper winding of wiperswitching relay 109 is ineffective at this time because the test wiper234 does not encounter a battery potential. Switch through relay 108,upon energizing, at armatures 150 and 158 connects the conductors 134and 137 through to the upper set of line wipers 230 and 232 and to theline conductors of the calling subscriber. At armature 151 switchthrough relay 108 completes a locking circuit for itself from groundedrelease trunk conductor 135 through its lower winding; at armature 152connects the grounded release trunk conductor 135 to test wiper 231 byway of normally closed springs controlled by armature 156, armature 152,conductor 172, and through test wiper 231 and its associated testcontact with which it is in engagement and through the two windings ofthe associated cut-off relay 'to maintam such cut-oit relay in energized'position and by way of the connector terminals of the associated linefor maintaining this calling line busy to connector switches havingaccess thereto. At armature 153 switch through relay 108 opens thecircuit to the rotary magnet, as previously described, and also connectsground to the common kick-oill conductor 181 for causing the allotter topreselect another idle finderselector link, as previously described. Thecalling'subscriber may now complete the vconnection to the desiredcalled subscriber in the well known manner.

After conversation and responsive to the calling subscriber replacingthe receiver ground isv removed from the holding conductor of theconnector switch in the well known manner whereupon the circuit of4 theswitching relay 101 of t-he selector is opened. Switching relay 101,upon deenergizing, at armature 122 completes a circuit for releasemagnet 112 of the selector SA and release magnet 113 of the inderFA asfollows: from ground by way of armature 122, armature 132 and itsresting contact, armature` 128 and its rest-ing contact, conductor 136,and by way of vertical off-normal springs 129 of the selectorandoff-normal springs 139 of the finder to release magnet 112 of theselector and release magnet 113 of the finder to battery. The operationof the release magnet 112 of the selector causes the selector SA toreturn to its normal position and at vertical o-normal springs 131 againconnects negative battery by way of resistance 130 and normally closedoff-normal springs 141 to guarding conductor 17 9 so that the test relay404 in the allotter may be energized to coniplete the start circuit forthe linder on another call. The operation of the release magnet 113 ofthe finder closes another point in the circuit for relay 404 throughvertical oil"- normal springs 1 41 and also closes a circuit extendingby way of grounded armature 122, armature 132, armature 128, conductor136, vertical off-normal springs 139, resistance 140, to busy commonconductor 177 for maintaining the busy common relay 405 in energizedposition. The circuits of both the release magnets are opened at theirrespective vertical oit-normal springs when the switches are fullyrestored.

The foregoing explains the normal operation of the apparatus incompleting calls. However, due to a calling subscriber abandoning callsafter completion of the vertical movement of the inder orvdue to somepossible fault the finder FA may operate its wipers in its rotarymovement beyond the contacts of any of the subscribers line. In thiscase when the wipers 230 to 235, inclusive, `are rotatedv beyond thebank contacts, cam springs 149 are closed and a circuit may be armature143 and its lower make traced for energizin the switch through relay 108as follows: rom ground by way of contact, up per winding of switchthrough relay'108, cam springs 149, and through the winding ot steppingrelay 106 to battery. The only f unction of switch through relay 108 atthis time to operate armature 153 which opens the circuit to the rotarymagnet 115 at its worklng contact and which closes a circuit fromgrounded start conductor 180 to the common kick-ofi" conductor 181 byway of its Working Contact for causing the allotter to kick-olf andpreselect another idle finder-selector link. In case the call was notabandoned this new preselected finder-selector link is taken intooperation and the connection completed in the same manner as previouslydescribed.

Referring again to the allotter shown in F ig. 4, and at a time when thestart relay 406 will now be assumed that negativebattery is notconnected to Gua-rd conductor 179 because the selector S or inder FA isin an olf-normal position or because of some fault. Under thesecircumstances the circuit for test relay 404 will not be completed and,therefore, the slow-to-operate relayv403 will have had time to fullyoperate. The circuit for energizing relay 403 may be traced as follows:from ground by way of armature 432, armature 424 and its restingcontact, through the upper winding of relay 403, kick-oit' conductor181, and through the winding of stepping magnet 407 to battery.Stepping'magnet 407 does not energize in the above traced circuit onaccount of the relatively high resistance of the upper winding of relay403. However, relay 403 upon energizing, at armature 421 an'd itsresting contact opens the short-circuit around the lower winding ofrelay 403 and at its working contact closes a circuit for energizing thestepping magnet 407 as follows: ground by way of armature 432, armature424 and its resting contact, through the lower low resistance winding ofrelay 403, armature 421 and its working contact, and through magnet 407to'battery. It may be stated that enough current flows through thewindings of relay 403 to maintain it in energized position at this time.Stepping magnet 407, upon energizing, at armature 428 opens the circuitof start relay 406 whereupon the start relay deenergizes. Start relay406, upon deenergizing, at armature 432 opens both the circuits of relay403 and magnet 407 whereupon relay 403 and the magnet deenergize. Thedeenergization of the magnet advances the wipers 408 to 410, inclusive,to the bank contacts ofthe next finder-selector link. In case thisfinder-selector link is busy, wiper 410 will encounter a groundpotential thereby causing magnet 407 to operate in a buzzer like. manneruntil an ungrounded contact is engaged by wiper 410.

has been energized responsive to a call, it

T his same ground connected by Way of wiper 410 maintains the startrelay 406 in shortcircuited condition. As soon as Wiper 410 loses groundstart relay 406 energizes and prepares the test circuit for test relay404. The same operation just described takes place in case Wiper 410 isengaged with a guarding conductor having no battery potential thereon.In case Wiper 410 engages a contact which terminates a guard conductorhaving battery potential thereon switching relay 404 is energized beforerelay 403 to complete the start circuit in the same manner as previouslydescribed.

Another condition which may arise is that the finder may not switchthrough within a predetermined time due to some fault. Considering thecause now in which a finder has been seized and operated but has failedto switch through within a predetermined time and, therefore, theallotter has not kicked off and has not opened the circuit to thevibrating relay 402. Under these conditions the vibrating spring 420after a predetermined time stops vibrating and is maintained in contactwith armature 419 whereupon the supervisory lockout relay 401 isenergized. `When this occurs relays 401,402, 404, 405 and 406 are inenergized position. At armature 418 relay 401 completes a lockingcircuit for itself extending by way of armature 531 of busy common relay505 of allotter DB, conductor 439, key 427 in operated position,armature 418, and through the winding of 401 to battery. At armature 417relay 401 opens a point in the circuit of busy common relay 405 so thatthis relay will deenergize when start relay 406 is later deenergized;and at armature 416 completes a circuit for operating the steppingmagnet 407 as follows: ground by way of armature 432, armature 424 andits Working contact, armature 416, kick-off conductor 181, and throughthe Winding of stepping magnet 407 to battery. Stepping magnet 407, uponenergizing, at armature 428 interrupts the circuit of start relay 406whereupon the start relay deenergizes. At armature 432 relay 406 opensth-e circuit of the stepping magnet 407 to cause the Wipers of theallotter to be advanced to the next finder-selector link, at armature433 prepares the preselecting circuit of the allotter, at armature 434opens the locking circuit of test relay 404 which deenergizes; opens thecircuit "I of busy comlnon relay 405 at armature 435 thereby causing thebusy common relay to release; and at armature 436 opens the circuit tothe vibrating relay 402. Busy common relay 405, upon deenergizing, atarmature 429 opens the circuit of start relay 406 as well as thepreselecting circuit, previously referred to; at armature 430 and itsworking contact, opens a further point in the circuit of start relay 406and at its resting contact connects the conductor 260 to conductor 261so that this particular call'and further calls from the subscribers -inthe A `roup will be taken care of by the allotter B and thefinderselector links in the B group. In addition relay 401 at armature440 closes an alarm circuit for operatin the alarm lam 441 associatedwith the a lotter DA and or operating the common alarm relay 442 tooperate a common alarm to call the exchange attendants attention to thefact that a fault has occured and that the allotter DA is locked out ofservice. The switchboard attendant may correct the fault or may operatekey 427 to release the supervisory lock-out relay 401 whereupon the busycommon relay 405 is again operated over the busy common lead in casethere are any idle finder-selector links. The operation of the busycommon relay 405 again renders the allotter available for use. Assumingnow that the attendant does not immediately free the allotter DA for useand further assuming that all of the finderselector links in the Bgroup, such as the finder-selector link FB and SB become busy then thebusy common relay 505 of the allotter DB in Fig. 5 will deenergize. Busycommon relay 505, upon deenergizing, at armature 530 transfers thecalling conductor 261 to conductor 260 so that all of the callsoriginating in the B group may be handled through the A group comprisingthe allotter DA and the finder-selector links such as FA and SA. Atarmature 531 relay 505 also opens the locking circuit of supervisorylockout relay 401, thereby causing relay 401 to deenergize and preparethe allotter DA for use in the same manner as previously described.

From the foregoing it will be seen that normally calls from the line Sare handled by the finder FA, and that in case all the finders in thegroup A are busy, calls from the lines in the A group, such as S, can behandled by the finder FB.

Assume now that at the time the substation S initiated a call, all ofthe finders in the group containing the finder FA are busy, in whichcase the call will be handled by the finders in the group containingfinder FB, provided no call is in progress at the time in the B group.It will be noted that the placing of ground on conductor 250 and thecontact 2 of the vertical bank VA also places ground upon Contact 9 ofthe vertical bank VB. It will also be noted that the banks of thefinders are slipped between group A and group B, so that the linesappearing in the lower half of the bank of group A appear in the upperhalt` of the bank of group B. Responsive to the grounding of conductor250, and in case all of the finder-selector links, such as FA and SA,are busy the busy common relay 405 will be in deenergized position and,therefore, the start relay 506 in the allotter DB is energized to starta finder in i;

group B, for exam le finder FB which operates 1n a vertical directionuntil the vertical wiper 263 encounters the marked bank contact, in thiscase the ninth bank contact in the vertical bank of VB. The wipers ofthe finder are stopped at this level and rotated in a horizontaldirection into engagement with the bank contacts of the calling line.Since the allotter DB and the finder-selector link FB and SB areidentical with the allotter DA and finder-selector link FA and SA it is,therefore, believed that no detailed description is necessary to-explainthis operation.

In a similar manner calls from the line S have as its first choice thefinders in the B group, such as the finder FB, in which its lineterminals appear in the second level, so that the wipers of FB are movedvertically two steps to engage the level containing the calling line S1.If, however, the group containing the finder FB is busy at the time thatS1 makes a call, that call will start the finder FA, provided there areno calls in progress at this time in the A group, and the line S will bepicked up b the finder FA which at this time must ta e nine verticafsteps to reach the level containing the calling line S. It will be notedthat the second bank contacts of the vertical bank VB is multipled tothe ninth bank contact to the vertical bank VA, so then when theconductor 252 is grounded responsive to the energization of the linerelay 203, level 2` of the vertical bank VB and level 9 of the bank VAare marked calling,

` so that whichever finder is started the call will stop on the properlevel when reached.

Having described the invention what is considered new and is desired tohave protected by Letters Patent will be set forth in the followingclaims:

l. In an automatic telephone system, a group of subscribers lines, agroup of finders having access to said lines, means including anallotter for preselecting an idle one of said finders, a timing deviceassociated with said.

V allotter, means in said allotter responsive to mined time,

the initiation of a call on one of said lines for initiating theoperation of said preselected finder and said timin device, means foroperating said finder to grid the calling line, means responsive tos thefinder finding the calling line for causing said finder to switchthroughand extend the connection from the calling line, means responsive to theswitchthrough operation of the finder for operating said allotter topreselect another idle finder in the group and for restoring said timingdevice, means for completely operating the timing device in case saidoperated finder does not switch-through within a predeterand meansresponsive to the completed operation of said timing device forrendering said allotter and finders inoperative to extend further calls.

2. In an automatic telephone system, 4a Igroup of subscribers linesagroup of finders aving access to said lines, means includin an allotterfor preselecting an idle one of sai finders, a timing device associatedwith Said allotter, means 1n said allotter responsive to the `initiationof a call on one of saidv lines for initiating the operation of saidpreselected finder and said timing device, means for operating saidfinder to find the calling line, means responsive to the finder findingthe calling line for causing said finder to switchthrough and extend theconnection from the calling line, means responsive to the switchthroughoperation of the finder for o erating said allotter to preselect anotherid e finder in the group and for restoring said timing device, means forcompletely operatin the timing device in case said operated der does notswitch-through within a predetermined time, means responsive to thecompleted operation of said timing device for advancing said allotter tothe next finder in the group and for rendering said allotter and findersinoperativeto extend further calls, a key associated with said allotter,and means responsive to the operation of said ke for restoring saidtiming device whereby said allotter and finders are again available foruse.

3. In an automatic telephone system, a group of subscribers lines, agroup of finders having access to said lines, means including anallotter foiipreselecting an idle one of said finders, a timing deviceassociated with said allotter, means in said allotter responsive to theinitiation of a call on one of said lines for initiating the operationof said preselected finder and said timin device, means for operatingsaid finder to hgnd the calling line, means responsive to the finderfinding the calling line for causing said finder to switchthrough andextend the connection from the calling line, means responsive to theswitchthrough operation of the finder for operating said allotter topreselect another idle finder in the group and for restoring said timingdevice, means for completely opera-tin the timing device in case saidoperated nder does not switch-through within a predetermined time, asecond group of finders having access to said lines and a secondallotter associated with said second group finders, and means responsiveto the completed operation of said timing device for advancing saidfirstV allotter to the next finder in the first group of finders, forrendering said first allotter and the first group finders inoperative toextend further calls, and for transferring the incompleted call of thecalling line to the second allotter and second finder group.

4. In an automatic telephone system, a group of subscribers lines, agroup of finders having access to said lines, means includin an allotterfor preselecting an idle one of sai finders, a timing device associatedwith said allotter, means in said allotter responsive to the initiationof a call on one of said lines for initiating the operation of saidpreselected finder and said timing device, means for operating saidfinder to find the calling line, means responsive to the finder findingthe calling line for causing said finder to switch-through and extendthe connection from the calling line, means responsive to theswitch-through operation of the finder for operating said allotter topreselect another idle finder in the group and for restoring said timingdevice, means for completely operating the timing device in case saidoperated finder does not switch through within a predetermined time, asecond group of finders having access to said lines and a secondallotter associated with said second group finders, means responsive tothe completed operation of said timing device for advancing said firstallotter to the next finder in the first group of finders, Jforrendering said first allotter and the first group of finders inoperativeto extend further calls, and for transferring the incompleted call ofthe calling line to the second allotter and second finder group, meansin said second allotter operative in case all the finders in said secondgroup are busy for restoring the said timing device in the firstallotter, and means res onsive to the restoration of said timing evicefor again rendering said first allotter and said first group findersavailable for use by calling subscribers.

5. In an automatic telephone system, a group of subscribers linesdivided into two sub-groups, two groups of nders, each group havingaccess to said lines, means including an allotter for each group offinders for preselecting an idle finderin its associated group, meanswhereby the first sub-group of lines are first choice to the firstfinder group and allotter and are normally served thereby and the secondsub-group of lines are first choice to the second finder group andallotter and are normally served thereby, a timing device associatedwith each of said allotters, means in each allotter responsive to theinitiation of a call in its associated sub-group of lines for initiatingthe operation of its associated preselected finder and for initiatingthe operation of its associated timing device, means for continuing theoperation of said finder to find the calling line, means responsive tothe finder finding the calling line for causing said finder toswitch-through and extend the connection from the calling line, meansresponsive to the switch-through operation of said finder for operatingrthe associated allotter to preselect another idle finder in the samegroup and for restoring the associated timing device before such deviceis completely operated, means for completing the operation of saidtiming device in case said operated finder does not switchthrough withina predetermined time, and means responsive to the operation of saidtiming'device for advancing said allotter to the next finder in the saidsame group of finders, for rendering said allotter and said same groupof finders inoperative to extend further calls, and for transferring theincompleted call of the said calling line to the other allotter and theother finder group.

G. In an automatic telephone system, a group of subscribers linesdivided into tWo sub-groups, two groups of finders, each group havingaccess to said lines, means including an allotter for each group offinders for preselecting an idle finder in its associated group, meanswhereby the first sub-group of lines are first choice to the firstfinder group and allotter and are normally served thereby and the secondsub-group of lines are first choice to the second finder group andallotter and are norlnally served thereby, a timing device associatedwith each of said allotters, means in each allotter responsive to theinitiation of a call in its associated sub-group of lines for initiatingthe operation of its associated preselected finder and for initiatingthe operation of its associated timing device, means for continuing theoperation of said finder to find the calling line, means responsive tothe finder finding the calling line for causing said finder toswitch-through and extend the connection from the calling line, meansresponsive to the switch-through operation of said finder for operatingthe associated allotter to preselect another idle finder in the sameroup and for restoring the associated timing evice before y such deviceis completely operated, lneans for completing the operation of saidtiming device in case said operated finder does not switch-throughwithin a predetermined time, means responsive to the operation of saidtiming device for advancing said allotter to the next finder in the saidsame group of finders, for rendering said allotter and said same groupof finders inoperative to extend further calls` and for transferring theincompleted callof the said calling line to the other allotter and theother finder group, means in said other allotter operative when all thefinders in said other group are busy for restoring the said operatedtiming device, and means responsive to the restoration of said timingdevice for again rendering said inoperative allotter and finder groupavailable for use by calling subscribers.

7. In an automatic telephone system, a group of subscribers7 lines, agroup of finders having access to said lines, means including anallotter having a motor magnet for preselecting an idle one of saidfinders, means in said allotter responsive to the initiation of `a callon one of said lines for initiating the operation of said preselectedfinder, means for lcontinuing the operation of said finder to find thecalling line, means responsive to the A finder finding the calling linefor causing said finderfto switch-throng and extend the connection fromthe calling line, a common kickoff conductor extending from all saidfinders direct to the motor magnet of said allotter, means responsive tothe switchthrough operation of the finder for operating said magnet oversaidconductor, and means in said allotter controlled by the operation ofsaid magnet for causing said allotter to preselect another idle finder.

8. In an automatic telephone system, a group of subscribers lines, agroup of finders having access to said lines, means including anallotter having a motor magnet for preselecting an idle one of saidfinders, means in said allotter responsive to the initiation of a callon one of said lines for initiating the operation of said preselectedfinder, means for continuing the operation of said finder to find thecalling line, means responsive to the finder finding the calling linefor causing said finder to switch-through and extend the connection fromthe calling line, a common kick-off conductor extending from all saidfinders direct to the motor magnet of said allotter, means responsive tothe switch-through operation of the finder for operating said magnetover said conductor, means in said allotter controlled by the operationof said magnet for causing said allotter to preselect another idlefinder, cam springs in said finder, means for operq ating said springsin case said finder fails to find the calling line and is operatedbeyond the lines of said group, and means for causing said finder toswitch-through and release responsive to the operation of said springs.

9. In an automatic telephone system, a group of subscribers lines, agroup of finders having access to said lines, means including anallotter having a motor magnet for preselecting an idle one of saidfinders, means in said allotter responsive to the initiation of a callon one of said lines for initiating the operation of said preselectedfinder, means including a stepping relay in said finder for operatingsaid finder to find the calling line, cam springs in said finder, aswitch-through relay in said finder, means for operating said camsprings in case said finder fails to find the calling line .and thefinder is operated beyond said group of lines, means responsive theretofor energizing said relays in a series circuit including said' operatedsprings, means responsive to the operation of said switchthrough relayfor releasing said finder and for operating the magnet of said allotter,and means in said allotter responsive to the energization of said magnetfor selecting another idle finder.

10. In an automatic telephone system, a group of subscribers lines, agroup of finders having access to said lines, an allotter having accessto said finders, a start conductor individual to each of said findersand terminating in said allotter, means including the motor magnet ofsaid allotter for operatin said allotter to preselect an idle one ofsaid finders, means in said allotter responsive to the initiation of acall o nl one of said lines for connecting a potential to the individualstart conductor of the preselected finder, means in said finderresponsive to' this potential for operating said finder to find thecalllng line, means in said finder responsive to the finder finding thecalling line for causlng sald finder to switch-through and extend theconnection from the callin line, a common kick-off conductor exten ingfrom all said finders direct to said motor magnet, means responsive tothe switch-throu h operation of the finder for operating sai magnet overa circuit including said individual start conductor and said commonkick-off conductor in series, and means in said allotter responsive tothe operation of said magnet for causing said allotter to preselectanother idle finder.

11. In an automatic telephone system, a group of subscribers lines, agroup of finders, the finders thereof having access to said lines, meansincluding an allotter for preselecting an idle one of said finders, astart relay in said allotter, means responsive to the initia- 'tion of acall on one of said lines for energizing said start relay, a test relayin said allotter energized responsive to the energization of said startrelay only in case the preselected idle finder is in normal position,and means responsive to the operation of said test relay for startingthe finder in the preselected link to find the calling line.

12. In an automatic telephone system, a. group of subscribers lines, agroup of finders, the finders thereof having access to said lines, meansincluding an allotter for preselecting an idle one of said finders, asta-rt relay in said allotter, means responsive to the initiation of acall on one of said lines for energizing said start relay, a test relayin said allotter energized responsive to the energization of said startrelay only in case the preselected idle finder is in normal position, athird relay in said allotter energized responsive to the energization ofthe start relay only in case said test relay fails to operate, and meanscontrolled by the energization of the third relay for causing saidallotter to select another idle finder-selector link.

13. In an automatic telephone system, a group of subscribers lines, agroup of' finders, the finders thereof havingaccess to said lines, meansincluding an allotter for preselecting an idle one of said finders, astart relay in said allotter, means responsive to the initiation of acall on one of said lines for energizing said start relay, a test relayin said allotter energized responsive to the energization idle finder isin normal position,means responsive to the operation of said test relayfor starting the finder in the preselected finder to find the callingline, a third relay in said allotter energized responsive to theenergization of the start relay only in case said test relay fails tooperate, a motor magnet in said allotter for operating the wipersthereof, means controlled by the operation of said third relay forenergizing said motor magnet, means controlled by said magnet fordeenergizing said start relay, means control-v led by the deenergizationof said start relay for deenergizing said third relay and said magnet,and means controlled by the deenergization of said magnet to step thewipers of said allotter to the next finder and to reenergize said startrelay in case such finder is idle.

14. In an automatic telephone system, a group of subscribers lines, agroup of finders, the finders thereof having access to said lines andhaving guarding conductors, an allotter having access to said finders byWay of said guard conductors, idle ones of said finders characterized bya distinct potential applied to their associated guard conductors whilethe busy ones of said finders are characterized by a different potentialapplied to their associated guard conductors, meansinsaid allotter forpreselecting a finder dependent upon the absence of said differentpotential on its associated guard conductor, mean s in said allotterresponsive to the initiation of a call on one of said lines for testingfor the presence of said distinct potential on the guard conductor ofthe preselected finder, and means in said allotter operative only caseno said distinct potential is found on the guard conductor of thepreselected finder for operating said allotter to select another finderfor use by the calling subscriber.

15. In an automatic telephone system, a group of subscribers lines, agroup of finders, the finders having access to said lines and havingguarding conductors an allotter having access to said finders by way ofsaid guard conductors, idle ones of said finders characterized by adefinite potential applied to their associated guard conductors whilethe busy ones of said finders are characterized by a different potentialapplied to their associated uard conductors, and means in said allotteror first testing for an absence of said different potential on theguard-conductors of the finders to preselect one of them, and thentesting for said definite potential on the guard conductor of thepreselected finder before seizing a finder for use by a calling one ofsaid subscribers lines.

16. In a telephone system, a finder switch having vertical and rotarymotions to find a calling line, a vertical magnet in the finder foroperating the finder in its vertical movement, a rotary magnet in thefinder for operating the finderin its rotary movement, means for closinga circuit to the vertical magnet to energize it, a single wound pulseending relay in said finder, means controlled by the vertical magnet inits energized position for energizing the pulse endlng relay to open thecircuit to the vertical magnet, a changeover relay in said finder, meansfor energizing the changeover relay in series with said pulse endingrelay, means controlled by the energization of the changeover relay fordeenergizing said pulse ending relay and for changing said circuitfrom'the vertical magnet to the rotary magnet to energize it, meanscontrolled \by the rotary magnet in its energized position forenergizing the pulse ending relay to open the circuit to the rotarymagnet, two test relays in said finder, means -for energizing either oneof said relays independent of said pulse ending relay, and meanscontrolled by the energized test relay independent of said pulse endingrelay for opening the circuit of the rotary magnet to stop the finder onthe calling line.

17. In a telephone system, a finder switch having a normally connectedand a normally disconnected set of Wipers, and having vertical androtary hunting movements to find a calling line in a group of lines, avertical magnet, a rotary magnet, and a stepping relay in said finder,means responsive to a call and including said relay and vertical magnetfor operating the Wipers of the finder step-bystep in its verticalmovement in search of the group of lines containing the calling line,means in the finder responsive to the finder finding the calling group.for stopping the Wipers opposite such group and for closing a circuitfor said rotary magnet, means including said circuit and said relay foroperating the rotary magnet to rotate the wipers stepby-step over thecontacts of said group in search of the contacts associated with thecalling line, a test wiper in each of said sets of Wipers, a wiperswitching relay in said finder, means responsive to one of said testwipers engaging'the test contact of the calling line for energizing saidwiper switching relay, and means controlled by said wiper switchingrelay for disconnecting the normally connected set of wipers and forconnecting up said normally disconnected set, and contacts on said wiperswitching relay for opening the circuit .to the rotary magnet to stopthe wipers on the calling line.

18. In a telephone system, a finder switch having a primary huntingmovement and a secondary hunting movement tofind a calling line in agroup of lines, a normally connected set of wipers and a normallydisconnected set of wipers in said finder, means responsive to a callfor associating a definite potential with the group of lines containingthe calling line, for associating a different potential with the testcontact of the calling line, and for initiating thel operation of saidfinder, means for operating said finder in its primary movenient insearch of said definite potential, means responsive to said finderencountering said definite potential for stopping the primary movementof said finder, a wiper switching relay in said finder, a secondarymagnet in said finder, a circuit for said magnet, means for operatingsaid magnet over said circuit to'operate the finder in its secondarymovement in search of said different potential, said wiper switchingrelay energizing responsive to the nder finding said different potentialfor disconnecting said normally connected set of Wipers and forconnecting up said normally disconnected set, and contacts on said wiperswitching relay for opening the circuit to the secondary magnet to stopthe wipers on the contacts of the calling line.

19. In an automatic telephone system, a subscribers line, a finderhaving access thereto, a primary test contact associated with said lineand normally maintained at battery potential, a secondary test contactassociated with said line and-normally maintained at zero potential, acut-oill relay associated with said line having two windings one ofwhich is of low resistance, means responsive to the initiation of a callon said line for applying a battery potential through the low resistancewinding of the cut-off relay to said secondary contact vand for applyingground potential to said primary contact to mark said line calling,wipers on said finder having access to said contacts, means in saidfinder controlled through said wipers to select said marked contacts andto establish a connection to said line, and means responsive to theestablishment of said connection for energizing said cut-ofi' relay tocomplete a holding circuit for itself including both of its windings inseries.

20. In a telephone system, a group of subscribers lines, a group offinders having access to said lines, a timing device common to thefinders, means responsive to a call on one of said lines for operatingan idle one of said finders to automatically hunt for and find thecalling line and for initiating the operation of said timing device,means responsive to the finder Ending the calling line for causing saidfinder to switch through and extend the connection from the callingline, means responsive to the switch-through operation of said finderfor restoring said timing device, and means for completely operatingsaid timing device to operate an alarm in case said operated finder doesnot switchthrough within a predetermined time.

21. In a telephone system, a group of subscribers lines, a group offinders having access to said lines, a timing device common to thefinders, means responsive to-a call on one of said lines for operatingan idle one of said finders to automatically hunt for and find thecalling line and for initiating the operation of Said timing device,means responsive to the finder finding the calling line for causing saidfinder to switch through and extend the connection from the callingline, means responsive to the switch-through op- `eration of said finderfor restoring said timing device, means for completely operating saidtiming device to operate an alarm in case said operated finder does notswitchthrough within a predetermined time, and moans responsive to thecompleted operation of. said timing device for rendering said group offinders inoperative to extend further calls.

22. In a telephone system, a group of subscribers lines, a group offinders having access to said lines, a timing device common to thefinders, means responsive to a call on one of said lines for operatingan idle one of said finders to automatically hunt for and find thecalling line and for initiating the operation of said timin device,means responsive to the finder fin ing the calling line for causing saidfinder to switch through and extend the connection from the callingline, means responsive to the switch-through operation o said finder forrestoring said timing device, means for completely operating said timingdevice to operate an alarm in case said operated finder does notswitchthrough Within a predetermined time, a second group of findershaving access to said lines, and means responsive to the completedoperation of said timing device for rendering said first group findersinoperative to extend further calls and for transferring the incompletedcall ofthe calling line and other calls lto the second finder group.

23. In a telephone system, a group of subscribers lines, a group offinders having access to said lines, a timing device common to thefinders, means responsive to a call on one of said lines for operatingan idle one of said finders to automatically hunt for and find thecalling line and for initiating the operation of said timing device,means responsive to the finder finding the calling line for causing saidfinder to switch through and extend the connection from the callingline, means responsive to the switch-through operation of said finderfor restoring said timing device, means for completely operating saidtiming device to operate an alarm in case said operated finder does notswitchthrough within a predetermined time, a second group of findershaving access to said lines, means -responsive to the completedoperation of said timing device for rendering said first group findersinoperative to extend `further calls and for transferring the(incompleted call of the calling line and other calls to the secondfinder group, means operative in case all said second group findersbecome busy for automatically restoring said timing device, and'meansresponsive to the restoration of said timing device for again renderingsaid first grou finders available for use by calling subscri rs.

24. In a telephone system a group of subscribers lines, a group of,finders having access to said lines, an allotter having access to saidfinders, a motor magnet in said allotter, a common kick-off conductorextending from all -the finders in the group direct to said motormagnet, means for initially operating said magnet over said conductor,and means in said allotter responsive to said initial operation of saidmagnet for thereafter operating said magnet and allotter to preselect anidle one of said finders.

25. In a telephone system, a group of subscribers lines, a group offinders having access to said lines, an allotter having access to saidfinders, a motor magnet in said allotter for operating said allotter -topreselect idle ones of said finders, a common kick-off conductorextending from all said finders direct to said motor magnet, a startconductor individual to each finder and terminating in said allotter,means for connecting a potential to one of said individual startconductors, and means for operating said magnet over a circuit includingsaid individual start conductor having said potential thereon and saidcommon kick-off conductor in series.

26. In a telephone system, a group of subscribers lines, a group offinders having access to said lines, an allotter having access to saidfinders, a motor magnet in said allotter for operatin the Wipers of saidallotter,a common kic off conductor extending from all said finders inthe group direct to said motor magnet, a test conductor individual toeach finder terminating in said allotter, a test Wiper in said allotterfor successively engaging said individual test conductors, two circuitsfor operating said magnet, the first circuit including said commonconductor and the second circuit including said individual testconductors, means for operating said magnet over said first circuit tooperate the Wipers of said allotter one step, and means responsivethereto for thereafter operating said magnet over said second circuit tooperate said allotter an indefinite number of steps in search of an idleone of said finders.

27. In a telephone system, a group of line finders, a'finder allotterhaving a test wiper, a start relay, and a motor magnet, a commonkick-ofi conductor extending from all said finders direct to said motormagnet, a circuit including said test wiper and motor magnet forintermittently operating said magnet to operate said allotterstep-by-step to preselect an idle one of said finders, means forenergizin said relay to open said circuit by disconnecting said magnetfrom said wiper, means for thereafter operating `said magnet overanother circuit including said common conductor, and said relaydeenergized responsive to the operation of said magnet over said commonconductor for reestablishing said first circuit.

28. In a telephone system, a group of subscribers lines, a group offinders having access to said lines, a guarding conductor for eachfinder, an allotter having access to said finders, means in saidallotter for making a first test over said guarding conductors topreselect an idle one of said finders, and means in said allotterresponsive to a call on \one of said lines for then making a second testover the guarding conductor of the preselected finder to seize andoperate said finder in case such nder is in normal condition.

29. In a telephone system, a group of subscribers lines, a group offinders having access to said lines, a guarding conductor for eachfinder, an allotter having access to said finders, means in saidallotter for making a first test over said guarding conductors topreselect an idle one of said finders, means in said allotter responsiveto a call on one of said lines for then making a second test over theguarding conductor of the preselected finder to seize and operate saidfinder in case such finder is in normal condition, and means in saidallotter responsive to the failure of said second test over saidguarding conductor for operating said allotter to select another idleone of said finders.

30. In a telephone system, a group of subscribers lines, a grou offinders, said finders having access to said ines,an allotter havingaccess to said finders, means in said allotter for making a first testto preselect an idle one of said finders, a relay in said allotter,means for energizing said relay responsive to a call on one of saidlines, and means in said allotter responsive to the cnergization of saidrelay for then making a second test to seize and operate saidpreselected finder in case said finder is in normal condition.

3l. In a telephone system, a group of subscribers lines, a group offinders, said finders having access to said lines, an allotter havingaccess to said finders, means in said allotter for makin a first test topreselect an idle one of said fingers, a relay in said allotter, meansfor energizing said relay responsive to a call on one of sald lines,means in said allotter responsive to the energization of said relay forthen making a second test to seize and operate said preselected finderin case said finder is in normal condition, and means in said allotterresponsive to the failure of said second test in case said finder is notin normal condition for operating said allotter to select another idleone of said finders.

32. In an automatic telephone system, an automatic subscribers linecircuit including the subscribers individual line, an individual linerelay, and a cut-0E relay having contacts ing a locking circuit foritself including both said windings in series.

33. In an automatic telephone system, a subscribers line, a cut-o relayindividual to said line having two windings, a finder having bankcontacts, wipers on said finder havving access to said line by way ofsaid contacts, means responsive to the initiation of a call on said'linefor marking said line calling in the bank of said finder and forstarting said finder, means' in said finder controlled through saidwipers for nding the marked line to establish a connection, and meansresponsive to the establishment of said connection for energizingsaid-cut-o relay over only one of its windings to complete a holdingcircuit for itself including both its windings in series. l

In witness whereof, I hereunto subscribe my name this 20th day ofJanuary, A. D.

NORMAN H. SAUNDERS.

